A Random-Access Column Object Model
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Key: HBASE-3851
URL: https://issues.apache.org/jira/browse/HBASE-3851
Project: HBase
Issue Type: New Feature
Components: client
Affects Versions: 0.92.0
Reporter: Karthick Sankarachary
Assignee: Karthick Sankarachary
Priority: Minor
Fix For: 0.92.0
By design, a value in HBase is an opaque and atomic byte array. In theory, any
arbitrary type can potentially be represented in terms of such unstructured yet
indivisible units. However, as the complexity of the type increases, so does
the need to access it in parts rather than in whole. That way, one can update
parts of a value without reading the whole first. This calls for transparency
in the type of data being accessed.
To that end, we introduce here a simple object model where each part maps to a
{{HTable}} column and value thereof. Specifically, we define a {{ColumnObject}}
interface that denotes an arbitrary type comprising properties, where each
property is a {{<name, value>}} tuple of byte arrays. In essence, each property
maps to a distinct HBase {{KeyValue}}. In particular, the property's name maps
to a column, prefixed by the qualifier and the object's identifier (assumed to
be unique within a column family), and the property's value maps to the
{{KeyValue#getValue()}} of the corresponding column. Furthermore, the
{{ColumnObject}} is marked as a {{RandomAccess}} type to underscore the fact
that its properties can be accessed in and of themselves.
For starters, we provide three concrete objects - a {{ColumnMap}},
{{ColumnList}} and {{ColumnSet}} that implement the {{Map}}, {{List}} and
{{Set}} interfaces respectively. The {{ColumnMap}} treats each {{Map.Entry}} as
an object property, the {{ColumnList}} stores each element against its ordinal
position, and the {{ColumnSet}} considers each element as the property name (as
well as its value). For the sake of convenience, we also define extensions to
the {{Get}}, {{Put}}, {{Delete}} and {{Result}} classes that are aware of and
know how to deal with such {{ColumnObject}} types.
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